Copper thin films are used as interconnects in semiconductor devices owing to the fact that copper has a very low resistivity of 1.67 μΩ·cm, a high resistance to electromigration and a high melting point. There have been reported studies of preparing such copper films by metal organic chemical vapor deposition (MOCVD) using cuprous organocopper compounds such as (hfac)Cu(vtms) (hfac=1,1,1,5,5,5-hexafluoro-2,4-pentanedionato, vtms=vinyltrimethylsilane) and cupric organocopper compounds such as Cu(hfac)2. In addition, Caulton et al. of Indiana University synthesized such a cupric organocopper precursor containing two β-ketoimine ligands with nitrogen donor moieties which are capable of forming dative bonds with copper [D. V. Baxter, K. G. Caulton, W.-C. Chiang, M. H. Chisholm, V. F. DiStasi, S. G. Dutremez, K. Folting, Polyhedron, 2001, 20, 2589].
However, it has been discovered that (hfac)Cu(vtms) has poor thermal stability, Cu(hfac)2 requires too high a decomposition temperature, and the copper β-ketoimine compound by Caulton et al. has relatively low volatility. Further, these conventional precursors are known to give copper thin films containing carbon or fluorine contaminants [V. M. Donnelly, M. E. Gross, J. Vac. Sci. Technol. A, 1993, 11, 66; and T. Gerfin, M. Becht, K. Dahmen, Mater Sci. Eng. B, 1993, 17, 97].
Besides the above-mentioned copper β-diketonate and β-ketoimine compounds, Davis et al. of Virginia Polytech. reported on the deposition of a copper thin film by way of effecting intramolecular β-hydrogen extraction of Cu(OCH2CH2NMe2)2, and recently, Chi et al., by intramolecular amine/imine conversion of Cu(OCCF3R1CH2NHR2)2 [V. L. Young, D. F. Cox, M. E. Davis, Chem. Mater., 1993, 5, 1701; and P.-F. Hsu, Y. Chi, T.-W. Lin, C.-S. Liu, A. J. Carty, S.-M. Peng, Chem. Vap. Deposition, 2001, 7, 28].
However, the conventional copper aminoalkoxide compounds have the problem that the purity of the formed copper thin film is unsatisfactorily low. Also, most of the reported compounds are solids at room temperature.